1. Field of the Invention
The present invention relates to a liquid crystal projector for displaying a picture on a screen by projecting light rays emitted by a light source onto three liquid crystal panels and transmitted by the three liquid crystal panels, and a projection lens unit, an optical unit and a cooling system to be employed in the liquid crystal projector.
2. Description of the Related Art
A prior art liquid crystal projector provided with three liquid crystal panels is disclosed in, for example, JP-A No. 6-289392. This prior art liquid crystal projector comprises, as principal components, a light source, a cold mirror, a blue light reflecting dichroic mirror (hereinafter referred to as “B light reflecting dichroic mirror”), a green light reflecting dichroic mirror (hereinafter referred to as “G light reflecting dichroic mirror”), image reflecting mirrors, a red-light liquid crystal panel (hereinafter referred to as “R liquid crystal panel”), a green-light liquid crystal panel (hereinafter referred to as “G liquid crystal panel”), a blue-light liquid crystal panel (hereinafter referred to as “B liquid crystal panel”), a combining dichroic prism and a projection lens. Light rays emitted by the light source are divided into R, G and B light rays by the light transmitting and reflecting agencies of the cold mirror, the B light reflecting dichroic mirror and the G light reflecting dichroic mirror, the light rays are reflected by the image reflecting mirrors toward the R, G and B liquid crystal panels. The light rays traveled through the R, G and B liquid crystal panels are combined by the dichroic prism and a color picture is projected through the projection lens in an enlarged color picture on a screen.
Such a known, commercialized liquid crystal projector employs three 1.3 in. liquid crystal panels. is formed in a compact construction and is capable of displaying pictures in a high definition.
The foregoing liquid crystal projector is provided with a cooling system for suppressing the temperature rise of the liquid crystal panels.
Referring to FIG. 1 showing a known liquid crystal projector in a side view, a cooling fan 81 (an axial fan in this liquid crystal projector) is disposed below three 1.3 in. liquid crystal panels (only liquid crystal panels 14 and 18 are shown) to blow air toward the liquid crystal panels including the liquid crystal panels 14 and 18 to suppress the temperature rise of the liquid crystal panels including the liquid crystal panels 14 and 18. Since the liquid crystal panels including the liquid crystal panels 14 and 18 are exposed directly to air delivered by the cooling fan 81, the liquid crystal panels including the liquid crystal panels 14 and 18 can effectively cooled. In FIG. 1, indicated at 27 is a projection lens.
The outside size in a horizontal plane of this liquid crystal projector provided with the three 1.3 in. liquid crystal panels excluding a projecting part of the projection lens projecting from a case is 245 mm by 329 mm, and the overall outside size in a horizontal plane of the liquid crystal projector including the projecting part of the projection lens is 245 mm by 380 mm. Such a large overall outside size of the liquid crystal projector is a problem in storing and carrying the liquid crystal projector, and the reduction of the overall outside size of the liquid crystal projector has been desired.
The inventors of the present invention examined a concept about miniaturization necessary to realize a liquid crystal projector more compact than the prior art liquid crystal projector and found that a liquid crystal projector provided with three liquid crystal panels must be formed in the smallest possible outside size suitable for storing the liquid crystal projector in a prevalently used storage cabinet and for carrying the same in a prevalently used carrying case.
The known liquid crystal projector shown in FIG. 1 has a height L2 equal to the sum of the height of a part including the projection lens 27 and the liquid crystal panels 14 and 18, and the height of the cooling fan 81. The liquid crystal projector has a dead space under the projection lens 27, which increases the overall height of the liquid crystal projector.